Elastic fluid turbine



Jan. 8, sA S CQOK ET AL4 ELASTIG FLUID TURBINE Filed Jan. 12, 1944 2 Sheets-sneek 1 ZZ l. I 1///////Zx/fj/j Jan.s,1946. s. s COOK ETAL l 2,392,463

ELASTIC FLUID TURBINE Filed Jan. l2, 1944 2 Sheets-Sheet 2 IOC BENDING MOMENTv 0N BLADE wlTHouT IMPACT INCREMENT 'OOPECO NDS T @wy-@W Patentedy Jan. 8, 1946 UNITED STATES PATENT OFFICE ELASTIC FLUID TURBINE Application January 12, 1944, Serial No. 517,946-

In Great Britain October 24, 1942 Claims.

This invention relates to partial admission impulse stages of elastic uid turbines, that is, to the type of such turbines in which the nozzles extend over only a part of the circumference. With such constructions, the blades enter and leave the elastic fluid stream from each group of nozzles once per revolution of the rotor and although each blade passage entering` this stream is gradually lled as it passes into the stream the time occupied in this filling process is so short that the leading blade forming the passage receives a considerable shock and in some cases blades have become damaged through this action after a comparatively short length of time in service;

Ihe object of the invention is to reduce the effect of this shock at entry into the stream.

The invention consists briefly in an elastic fluid turbine of the type indicated above wherein the rst nozzle or lirst few nozzles of a group of nozzles which the blades pass on entering the group is or are of such form that the elastic fluid stream issuing therefrom gradually increases in radial depth from the point where the blades iirst enter this stream.

Referring to the accompanying diagrammatic drawings:

Figure l is an end elevation of a group of nozzles embodying the present invention looking in the direction of arrow A of Figure 2, which is a partial developed section on the line XX of Figure l, and

Figures 3 and 4 are modied forms of the end jets of the nozzle, and

Figure 5 depicts three graphs connecting bending moments on a blade with times when the blade rst enters the elastic fluid stream.

In carrying the invention into effect according to one convenient form illustrated by way of example in Figures 1 and 2, we provide a first nozzle a Iof a group of nozzles with a uniformly increasing radial depth commencing from zero at a point b where thel rotor blades c enter the stream, the radial depth being unsymmetrical about the mean circumference of the jets.

The radial depth of the last nozzle d of the group decreases towards the end e of the group at which the rotor blades leave the stream.

In an alternative arrangement illustrated in Figure 3, the variation in depth takes place over the first two nozzles af of a group of nozzles and the variation is symmetrical about the mean circumference.

In a further alternative arrangement illustrated in Figure 4 the variation is symmetrical about the mean circumference but takes place over the first nozzle a only.

Figure 5 illustrates, for three types of nozzles, the bending moment M on a turbine blade caused by the nozzle jet; impinging thereon, plotted to a base T of time from the moment when the blade iirst encounters the elastic fluid stream. Curve A is for an ordinary type nozzle of which the rst jet is of the full radial depth and the bending moment on the blade increases rapidly from the point 0 where it enters the stream to the full value. In this case the time in which the bending moment increases from G to is the time occupied by the blading moving a distance equal to one blade pitch. Curve B shows the rate of increase of the bending moment for the form shown in Figure 4 and curve C shows the rate of increase for the form shown in Figure l.

The radial depth of the last nozzle d of the group decreases towards the end e of the group at which the rotor blades leave the stream,

We claim:

l. In an elastic uid turbine, a partial admission impulse stage having a group of nozzles with independent flow into the blade passage, and with the nozzles of the group chiefly of uniform radial depth throughout, wherein the rst nozzle of the group which the blades pass on entering the group is formed with its inner wall of substantially constant radial taper enlarging the fluid passage from the point where the blades first come into register with said iirst nozzle, whereby a gradually increasing radial depth oi the fluid passage through said nozzle is provided.

2. In an elastic fluid turbine, a partial admis.- sion impulse stage having a group of nozzles with independent flow into the blade passage, and with the nozzles o-f the group chiey of uniform radial depth throughout, wherein the first few nozzles of the group which the blades pass on entering the group are formed with their inner Walls of substantially constant radial taperenlarging the iiuid passage from the point where the blades rst come into register with said rst nozzle, whereby fluid passages of gradually in creasing radial depth through said first few nozzles are provided.

3. An elastic fluid turbine as claimed in claim 1, wherein the increase in radial depth of the fluid passage commences from zero at a point Where the rotor blades first come into register with said first nozzle.

4. An elastic fluid turbine as claimed in claim 1, wherein the increase in radial depth of the ud passage is symmetrical about the mean circumference of the fluid passage.

5. An elastic fluid turbine as claimed in claim 1, wherein the last nozzle of a group of nozzles has its inner wall of substantially constant radial taper decreasing the fluid passage towards the end of the group with which the rotor blades last remain in register, whereby a gradual decrease in radial depth of the fluid passage through said last nozzle is provided.

SIIANLEY SMITH COOK. LOUIS MORTIMER DOUGLAS. 

